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MSU ECE 4532 - Test Specifications

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4.3 Test Specification – Software4. EvaluationIn order to ensure that our system meets the design constraints, each sub-system will be tested in its entirety. The figure below illustrates the fundamental design. The microcontroller and PICs are software based, and the battery packs, monitor circuits, and power supply are hardware components. Testing proper functionality of all these components is important since the system will be handling large currents (up to 250 amps) and large voltages (up to 300 volts). These can pose as potential risks to the driver of the car, and care will be taken to ensure that our system is as safe as possible. Figure 4.1 Design ConceptThe figure above represents the concept of our design. The microcontroller obtains measurements from the PICs and monitor circuits. The monitor circuits take measurements of battery pack characteristics such as voltage, temperature, and current. The power supply provides the system with power, and also provides the power needed to recharge the batteries. The rest of this document describes the plans for testing out system. Testing and Simulation Equipment1. Computerized Battery Analyzer2. Digital Multi-meter3. Voltage Source4. PSpice5. High Resistant Load6. MaxPlus7. RS232 Interface8. Thermometer9. MatLab4.1 Test Specification-SimulationSimulation is needed to obtain realistic values to compare with calculated or theoretical values. The realistic values will be used to determine the accuracy of the design.MicrocontrollerPICSMonitorCircuitsBattery PacksPower Supply4.1.1 Monitoring CircuitThe battery monitoring circuit observes two characteristics of the batteries namely the state of health (SOH) and state of charge (SOC). This circuit will be drawn and simulated in PSpice to obtain expected values of the different components of the circuit. Voltage and current readings at key location will be analyzed for comparison with calculated values. Accuracy of the design will be assessed by the variation in calculated and simulated values. Procedure:1. Draw circuit in PSpice.2. Analyze the simulated voltage and current.3. Verify that simulation results match expected values.4. Adjust circuit design as necessary.The results of this simulation will aid us in constructing the monitor circuit correctly.4.2 Test Certification – HardwareThe system’s hardware consists of the battery packs, the monitor circuits, and the power supply. Each will be tested in order to ensure proper functionality.4.2.1 Battery PacksThe battery packs will be individually tested using the Computerized Battery Analyzer (CBA). Temperature, voltage, and current of the battery packs will be measured as they discharge; this data will be imported to a computer through a universal serial bus. After each battery pack completes a discharge cycle, the data will be displayed to the screen graphically via the CBA software package. These results will be used to qualify the manufacture’s specifications; as well as, produce measurements to compare with theoretical characteristics of nickel metal hydride batteries. Procedure:1. Place single battery pack on the test bed.2. Configure battery pack and CBA.3. Connect CBA and laptop computer together.4. Discharge battery with 5.6 Ω load.5. Interpret graphical data.6. Repeat for loads of 2.9 Ω, 1.9 Ω, and 1.4 Ω.7. Verify that discharge data is consistent among the different battery packs and loads.Consistent operation of the battery packs is pertinent to our design since much of our design is based on estimates of the state-of-charge. To make an accurate estimate, the battery packs must be predictable. This data will tell us how the battery-packs behave.4.2.2 Monitor CircuitsThe monitor circuits will be tested by testing three different sub-circuits: the voltage measurement circuit,the current measurement circuit, and the temperature measurement circuit. Three tests will ensure that the values measured will be readable by the A/D converter on the PIC. 4.2.2.1 Voltage MeasurementsSince the nominal voltage across the battery packs is 12 volts, and the voltage range for the A/D is 5 volts, the voltage across the battery packs will have to be scaled down in order to be read properly by the A/D. The monitor circuit will accomplish this using a simple voltage divider. In order to test this, a voltage source will be used to simulate the battery pack.Procedure:1. Set voltage source to 12 volts.2. Apply voltage to voltage divider.3. Measure reduced voltage.4. Verify that voltage is 5 volts.5. Set voltage source to 6 volts.6. Measure reduced voltage.7. Verify that voltage is 2.5 volts.This data will be used to ensure that the voltages measured by the A/D do not exceed the circuit’s limitations. 4.2.2.2 Current MeasurementsThe system will measure high currents using a Hall Effect current sensor. This sensor will be able to accept high currents (up to 400 amps) and convert them into a smaller current that can be read by the A/D on the PIC. Procedure1. Apply 5 amps to current sensor.2. Measure and note output current.3. Verify that output translates to 5 amps.4. Apply 10 amps to current sensor.5. Measure and note output current.6. Verify that output translates to 10 amps.7. Verify that differences in output currents are proportional to the differences in input currents. 8. Repeat for consecutively higher currentsThis data will be used to ensure that the currents measured by the A/D do not exceed the circuit’s limitations. 4.2.2.3 Temperature MeasurementsThe thermistors will be tested by simply varying its temperature and measuring the corresponding resistance. Procedure1. Verify that room temperature (25ºC) resistance is 800Ω.2. Increase temperature.3. Verify that resistance increases.4. Increase temperature to 50ºC.5. Verify that resistance is 1.6kΩ.This data provides us with behavioral information about the thermistors that will be used to measure temperature. The thermistors must be accurate enough to obtain an accurate temperature measurement.4.2.3 Power SupplyThe power supply will be tested by testing its two output voltages: 12 volts and 5 volts.Procedure 1. Couple 5 volt output to multimeter. 2. Verify that power supply provides 5 volts. 3. Couple 12 volt output to multimeter. 4. Verify that power supply provides 12 volts.Since the power supply is responsible for making sure our system stays alive, the proper operation of


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